A refractory plate brick is used in a sliding nozzle device for controlling a flow rate of molten steel. The plate brick is commonly made using an alumina-carbon based material, and classified broadly into an unburned product and a burned product according to a production method therefor. Generally, the unburned product is produced by, after a shaping process, performing a heat treatment at a temperature of 100 to 300° C. The burned product is produced by performing a burning process at a high temperature of 1000° C. or more, and, after the burning process, performing an impregnation treatment with pitch, tar or the like.
However, the above plate bricks have a problem that they generate smoke and a pungent odor during use. This is because the unburned product generates a decomposition gas of a phenol resin as a binder, and the burned product generates a decomposition gas of tar or the like as an impregnant.
Therefore, a so-called soft-burned product to be produced by performing a heat treatment at a temperature of 400 to 1000° C., i.e., a temperature intermediate between the above temperatures, was studied as a plate brick with less generation of the decomposition gas.
For example, the following Patent Document 1 discloses a production method which comprises kneading and forming a mixture of a refractory raw material, a phenol-based resin and an aluminum powder consisting of atomized spherical particles to obtain a shaped body, and then subjecting the shaped body to a heating treatment at a temperature of 550 to 650° C. The Patent Document 1 describes as follows. If the heating treatment temperature is less than 550° C., oxidation resistance of the phenol-based resin becomes inferior, and a decomposition gas of the phenol-based resin is generated to cause odor during use. If the heating treatment temperature is greater than 650° C., aluminum carbide will be formed. If aluminum carbide is formed, it easily reacts with water under normal temperature and normal pressure to form aluminum hydroxide, which involves a volume expansion and an increase in weight. Thus, it is highly likely that an obtained plate brick will crumble during storage.
The following Patent Document 2 discloses a technique of adding a phenol resin to a mixture consisting of 90 to 99.5 weight % of aggregate of a refractory inorganic material, and 0.5 to 10 weight % of aluminum or aluminum alloy fiber, and subjecting the mixture to a heat treatment at 700° C., 850° C. or 1000° C. The Patent Document 2 described as follows. Based on performing the heat treatment at a temperature equal to or greater than a melting point of the aluminum or aluminum alloy (as for aluminum, 660° C.), aluminum can be infiltrated between grains of a peripheral microstructure to dramatically improve strength of a refractory product and significantly enhance spalling resistance of the refractory product. If the heat treatment temperature is greater than 1000° C., desired characteristics as a fiber cannot be maintained, so that a difference in characteristics between a fiber and a powder will be lost. Moreover, along with progress of the aluminum infiltration, a void occurs in an area where the fiber has existed, so that it is rather likely that corrosion/erosion resistance will deteriorate.
The following Patent Document 3 discloses a production method which comprises: preparing a refractory inorganic raw material, a carbon-based raw material and a metal-based raw material to allow the raw materials to form a continuous particle size distribution having a particle size of 0.1 to 4000 μm; adding a phenol resin to the raw materials; and burning the mixture in a non-oxidizing atmosphere at a temperature of 800 to 1500° C., wherein no impregnation treatment is performed. The Patent Document 3 also discloses a refractory product subjected to a burning process at 850° C. and having an apparent porosity of 5.0%, as one example.    [Patent Document 1] JP 2000-94121A    [Patent Document 2] JP 1-313358A    [Patent Document 3] JP 11-199328A